All Solid-state Eye-safe Raman Lasers

1.5μm laser has a wide range of applications in lidar, laser ranging, atmospheric remote sensing and spatial optical communications because it has a relative high eye damage threshold and is in the "atmospheric window". A first-Stokes Raman laser of 1.5μm can be obtained pumped by 1.3μm. High-power 1.3μm laser has a great deal of applications in laser medicine, fiber communications system, non-linear frequency conversion and so on. Nd:YAP crystal has many properties that has been proven as one of the most favorable candidates for 1.3μm, because of its large emission cross-section at 1.34μm. Another feature of Nd:YAP crystal is the strong natural birefringence,which makes the output of linearly polarized beam radiation and effectively inhibit the influence of the thermal induced depolarization under high-power pumping.In this paper, output characteristics of Ba(NO3)2 Raman crystal excited by 1.08μm and 1.34μm based on a QCW diode-side-pumped actively E-O Q-switched Nd:YAP laser was studied. We analyzed characteristics of the flat-flat cavity and flat-concave cavity using the ABCD transfer matrix to produce efficient output of 1.34μm. Using an external cavity, 1.5μm eye-safe Raman laser was obtained with Ba(NO3)2 crystal.The SRS characteristics of Ba(NO3)2 crystal was also studied. Three Stokes Raman lasers were observed under the single-pass SRS generator pumped by 1.08μm based on the Nd:YAP laser. The main contents of this dissertation was summarized as follows:(1) A diode side-pumped Nd:YAP laser that can produce single pulse energy of 19.2mJ and 18.3mJ of 1.34μm output under the flat-flat cavity and flat-concave cavityat a repetition rate of 20 Hz. A BBO crystal was used as E-O Q-switched crystal and there was no polarizer in the resonator. The 38 ns pulse width of 1.34μm was obtained width the repetition rate of 20 Hz under the flat-flat cavity. The output characteristic of 1.08μm was also experimentally researched and the largest single pulse energy of 48.6mJ and pulse duration of 27 ns was obtained at a repetition rate of 20 Hz under the same flat-flat cavity.(2) The output wavelength of the single-pass SRS generator was at 1218.50 nm, 1396.87 nm and 1637.25 nm pumped by 1080 nm based on a Ba(NO3)2 crystal with a size of 8mm×8mm×50mm. Only the first Stokes laser of 1562 nm was obtained pumped by 1344 nm both under single-pass SRS generator and an external cavity. When the pump laser was operated at 19.2mJ, a maximum Raman output energy of 1.83 mJ at a repetition rate of 20 Hz was obtained, corresponding to an overall optical to optical(1.34μm to 1.56μm) conversion efficiency of 9.53% under an external cavity of Nd:YAP/Ba(NO3)2 Raman laser. The pulse width of the Raman pulses at the wavelength of 1.56μm was reduced to 9ns compared to the pump pulse width of 38 ns at the wavelength of 1.34μm.